Vulnerability-Lookup

CVE-2026-52734 (GCVE-0-2026-52734)

Vulnerability from cvelistv5 – Published: 2026-08-18 19:19 – Updated: 2026-08-19 18:20

Title

ZEBRA: Unbounded memory leak in mempool download pipeline via timeout path cancel_handles retention

Summary

ZEBRA is a Zcash node written entirely in Rust. Prior to 4.5.0, an unauthenticated P2P peer can cause the mempool download pipeline to retain transactions after verification reaches the outer RATE_LIMIT_DELAY timeout. In zebrad/src/components/mempool/downloads.rs, Downloads::poll_next removed cancel_handles entries after success and ordinary verification errors, but tokio::time::error::Elapsed did not carry the UnminedTxId needed to remove the timed-out entry. Each retained cancel_handles entry could hold a full Gossip::Tx(UnminedTx), while normal mined-transaction cleanup could not match attacker transactions and no periodic garbage collection or count cap existed. Sustained traffic therefore caused monotonic memory growth until swap pressure degraded the node or the operating system terminated the zebrad process for exhausting memory. This issue is fixed in version 4.5.0.

Severity

5.3 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-19 18:17 UTC

CWE

CWE-401 - Missing Release of Memory after Effective Lifetime

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7613 records in the last 180 days details

References

3 references

URL	Tags
https://github.com/ZcashFoundation/zebra/security…	x_refsource_CONFIRM
https://github.com/ZcashFoundation/zebra/commit/1…	x_refsource_MISC
https://github.com/ZcashFoundation/zebra/releases…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
ZcashFoundation	zebra	Affected: < 4.5.0	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-52734

Vulnerability from fkie_nvd - Published: 2026-08-18 20:17 - Updated: 2026-09-09 21:13

Severity

5.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/ZcashFoundation/zebra/commit/1440b43ca7df59aca948090d45117557b217a6cd
	security-advisories@github.com	https://github.com/ZcashFoundation/zebra/releases/tag/v4.5.0
	security-advisories@github.com	https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-65jj-fmw8-468q

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "zebra",
          "vendor": "ZcashFoundation",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 4.5.0"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
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    {
      "lang": "en",
      "value": "ZEBRA is a Zcash node written entirely in Rust. Prior to 4.5.0, an unauthenticated P2P peer can cause the mempool download pipeline to retain transactions after verification reaches the outer RATE_LIMIT_DELAY timeout. In zebrad/src/components/mempool/downloads.rs, Downloads::poll_next removed cancel_handles entries after success and ordinary verification errors, but tokio::time::error::Elapsed did not carry the UnminedTxId needed to remove the timed-out entry. Each retained cancel_handles entry could hold a full Gossip::Tx(UnminedTx), while normal mined-transaction cleanup could not match attacker transactions and no periodic garbage collection or count cap existed. Sustained traffic therefore caused monotonic memory growth until swap pressure degraded the node or the operating system terminated the zebrad process for exhausting memory. This issue is fixed in version 4.5.0."
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GHSA-65JJ-FMW8-468Q

Vulnerability from github – Published: 2026-07-02 20:12 – Updated: 2026-07-02 20:12

Summary

zebrad has unbounded memory leak in mempool download pipeline via timeout path cancel_handles retention

Details

Am I affected

You are affected if:

You run zebrad up to and including v4.4.1.
Your node accepts inbound P2P connections (network.listen_addr is set, which is the default).
Your node's mempool is active (node is synced near the chain tip).

All default configurations are affected.

Summary

The mempool download pipeline's cancel_handles map retains entries for transactions whose verification times out at the outer RATE_LIMIT_DELAY (73-second) boundary. The tokio::time::error::Elapsed error carries no payload, so the transaction ID is unrecoverable and the corresponding cancel_handles entry (including the full Gossip::Tx(UnminedTx), up to ~2 MB) is never removed. Entries accumulate monotonically with no upper bound or garbage collection, leading to eventual out-of-memory process termination.

Details

Downloads::poll_next() at zebrad/src/components/mempool/downloads.rs:215-228 handles three terminal states for a verification task:

Ok(Ok(...)): success. Calls cancel_handles.remove(&tx.transaction.id). Correct.
Ok(Err(...)): verification error. Calls cancel_handles.remove(&hash). Correct.
Err(elapsed): outer timeout. Returns Err(elapsed) without removing anything. Bug.

tokio::time::error::Elapsed has no payload, so the timed-out transaction's UnminedTxId is unrecoverable from the error. The consumer at zebrad/src/components/mempool.rs:663-672 explicitly acknowledges this gap with a TODO comment.

The only cleanup paths for cancel_handles are cancel(mined_ids) (removes entries matching mined transaction IDs; attacker transactions are never mined) and cancel_all() (clears everything on shutdown or chain reset). No periodic GC, no time-based eviction, and no count cap exists.

For direct tx pushes (Gossip::Tx), the retained entry holds the full deserialized transaction, which can be up to ~9 MB in memory for a transaction near the transparent-output extreme. Per-connection leak rate at worst case: ~685 KB/s (~2.4 GB/hour).

Patches

The fix preserves the UnminedTxId through the timeout error path: wrap the timeout future so the spawned task's outer error carries the txid (e.g., Err((txid, elapsed))). In Downloads::poll_next(), on the timeout arm, call cancel_handles.remove(&txid).

Workarounds

There is no configuration-level workaround. Restarting the node clears the accumulated entries. Operators running in memory-constrained environments (containers with cgroup limits) may see the process killed by the OOM killer before natural recovery.

Impact

Gradual, unbounded memory exhaustion of a Zebra node from unauthenticated P2P traffic. The leak is monotonic (entries are never freed under normal operation) but slow (~685 KB/s per connection worst case). An attacker must sustain traffic for hours to exhaust typical server memory. The node continues operating normally until memory pressure becomes critical, at which point the OS OOM killer terminates the process or the node degrades due to swap pressure. No consensus impact, no fund loss, no on-disk corruption.

Credit

Reported by @AnticsDecoded via a private GitHub Security Advisory submission. Working E2E reproduction on a live regtest node with staged parent/child transaction dependencies.

Severity

5.3 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 4.4.1"
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "zebrad"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.5.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-52734"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-401"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-02T20:12:35Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Am I affected\n\nYou are affected if:\n\n1. You run `zebrad` up to and including `v4.4.1`.\n2. Your node accepts inbound P2P connections (`network.listen_addr` is set, which is the default).\n3. Your node\u0027s mempool is active (node is synced near the chain tip).\n\nAll default configurations are affected.\n\n### Summary\n\nThe mempool download pipeline\u0027s `cancel_handles` map retains entries for transactions whose verification times out at the outer `RATE_LIMIT_DELAY` (73-second) boundary. The `tokio::time::error::Elapsed` error carries no payload, so the transaction ID is unrecoverable and the corresponding `cancel_handles` entry (including the full `Gossip::Tx(UnminedTx)`, up to ~2 MB) is never removed. Entries accumulate monotonically with no upper bound or garbage collection, leading to eventual out-of-memory process termination.\n\n### Details\n\n`Downloads::poll_next()` at `zebrad/src/components/mempool/downloads.rs:215-228` handles three terminal states for a verification task:\n\n- `Ok(Ok(...))`: success. Calls `cancel_handles.remove(\u0026tx.transaction.id)`. Correct.\n- `Ok(Err(...))`: verification error. Calls `cancel_handles.remove(\u0026hash)`. Correct.\n- `Err(elapsed)`: outer timeout. Returns `Err(elapsed)` without removing anything. **Bug.**\n\n`tokio::time::error::Elapsed` has no payload, so the timed-out transaction\u0027s `UnminedTxId` is unrecoverable from the error. The consumer at `zebrad/src/components/mempool.rs:663-672` explicitly acknowledges this gap with a TODO comment.\n\nThe only cleanup paths for `cancel_handles` are `cancel(mined_ids)` (removes entries matching mined transaction IDs; attacker transactions are never mined) and `cancel_all()` (clears everything on shutdown or chain reset). No periodic GC, no time-based eviction, and no count cap exists.\n\nFor direct `tx` pushes (`Gossip::Tx`), the retained entry holds the full deserialized transaction, which can be up to ~9 MB in memory for a transaction near the transparent-output extreme. Per-connection leak rate at worst case: ~685 KB/s (~2.4 GB/hour).\n\n### Patches\n\nThe fix preserves the `UnminedTxId` through the timeout error path: wrap the timeout future so the spawned task\u0027s outer error carries the txid (e.g., `Err((txid, elapsed))`). In `Downloads::poll_next()`, on the timeout arm, call `cancel_handles.remove(\u0026txid)`.\n\n### Workarounds\n\nThere is no configuration-level workaround. Restarting the node clears the accumulated entries. Operators running in memory-constrained environments (containers with cgroup limits) may see the process killed by the OOM killer before natural recovery.\n\n### Impact\n\nGradual, unbounded memory exhaustion of a Zebra node from unauthenticated P2P traffic. The leak is monotonic (entries are never freed under normal operation) but slow (~685 KB/s per connection worst case). An attacker must sustain traffic for hours to exhaust typical server memory. The node continues operating normally until memory pressure becomes critical, at which point the OS OOM killer terminates the process or the node degrades due to swap pressure. No consensus impact, no fund loss, no on-disk corruption.\n\n### Credit\n\nReported by `@AnticsDecoded` via a private GitHub Security Advisory submission. Working E2E reproduction on a live regtest node with staged parent/child transaction dependencies.",
  "id": "GHSA-65jj-fmw8-468q",
  "modified": "2026-07-02T20:12:35Z",
  "published": "2026-07-02T20:12:35Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-65jj-fmw8-468q"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/ZcashFoundation/zebra"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ZcashFoundation/zebra/blob/d4cd662c716382f6397d2a730148025a1ca79fec/zebrad/src/components/mempool.rs#L663-L672"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ZcashFoundation/zebra/blob/d4cd662c716382f6397d2a730148025a1ca79fec/zebrad/src/components/mempool/downloads.rs#L215-L228"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "zebrad has unbounded memory leak in mempool download pipeline via timeout path cancel_handles retention"
}

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CVE-2026-52734 (GCVE-0-2026-52734)

FKIE_CVE-2026-52734

GHSA-65JJ-FMW8-468Q

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